1. Field of the Invention
The present invention relates to a method of processing a measured value, and more particularly, to a method for obtaining a directing measured result by integrating a number of measured values, for example, image information in pixel units handled in an image processing or voice information in time series handled in an voice processing. This invention further relates to a shape reconstructing method using said method, and an apparatus suitable for implementing said shape reconstructing method.
2. Description of the Related Art
As an example of a method for detecting surface inclinations of a subject in pixel units and reconstructing a shape of the subject by integrating the detected inclinations, there is a method disclosed in reference I "THE TRANSACTIONS OF THE INSTITUTE OF ELECTRONICS, INFORMATION, AND COMMUNICATION ENGINEERS OF JAPAN, PART D-II VOL. J77-D-II NO.9 pp.1797 to 1805, SEPTEMBER 1994". This method obtains plural images of a subject by photographing said subject from a fixed position as changing only the direction of a light source. Next, it detects surface inclinations of said subject in pixel units from pairs of luminances on arbitrary pixels corresponding to each other in these images. And it reconstructs a shape by integrating the detected inclinations (see "lines 1 to 9 in the left column of pp.1798 of the reference I"). When performing this integration, it is necessary to determine integral intervals. This is for the purpose of distinguishing an object to be photographed in a subject from its background.
As a method for determining an integral interval, there have been up to now (a) a method of separating an integral interval from an image by means of a two-level processing or the like (see "Line 5 from the bottom of pp.1799 of the reference I") and (b) a method of identifying an integral interval by comparing a subject with a reference object on the basis of a reflectivity map and estimating a domain different in reflectivity on the basis of an estimated error value of a pixel normal vector (see "Line 4 of pp.1799 to line 1 of pp.1800 of the reference I").
And for performing the integration, a method has been adopted (1) which uses the brightest point in an image as an initial value for the integration (see "Lines 9 and 10 of pp.1800 of reference I") or (2) which performs integration after obtaining an integration starting point to minimize an error of an initial inclination value (see reference II "THE TRANSACTIONS OF THE INSTITUTE OF ELECTRONICS, INFORMATION, AND COMMUNICATION ENGINEERS OF JAPAN, PART D-II VOL. J76-D-II NO.10, line 28 or later in the left column of pp.2244).
And in order to suppress accumulation of integral errors, a method is also adopted which computes average values of depth as weighting with estimated errors (see "Lines 19 and 20 in the left column of pp.1800 of reference I").
And in order to reduce an integral error, a method is also adopted which selects an integral path (see "Line 3 or later from the bottom of the left column of pp.2244 of reference II").
However, the prior art adopts a method of simply integrating inclinations on pixels as integration itself. Therefore, since noises and quantizing errors are accumulated, there has been a disadvantage that an integral error is liable to become great. Concretely, for example, in an existing method, single-shot noises or quantizing noises often caused by photographing a subject by means of a CCD (charge coupled device) camera or the like are accumulated as an integral error.
In case of adopting a method of weighting with estimated errors in order to suppress accumulation of integral errors, if estimation of errors is wrong, an integrated value is distorted by the errors, and since an amount of suppression varies with a quantity of estimated errors, an integrated value is distorted by the variation in suppression.
In case of adopting a method of selecting an integral path in order to reduce integral errors, it is not easy to select a proper integral path and integrated values are made different depending upon the selected paths.
One object of the present invention is to provide a measured value processing method capable of easily reducing accumulation of integral errors without performing such a human work as an error estimation and an integral path selection.
Another object of the present invention is to provide a shape reconstructing method and an apparatus using this processing method.
A further object of the present invention is to provide an apparatus for implementing the shape reconstructing method.